Process and apparatus for surfacing plate glass



M55 15, 1934- F. v. WILHELM ET Ax. 1,959,225

' PROCESS AND APPARATUS FOR 'SURFACING PLATE GLASS Filed Sept. l, 1933 3 Sheets-Sheet l INVENTOR5 A RNEYS.

May 15, 1934- F. v..w|LH|-:| M r AL y1,959,225

PROCESS AND 'APPARATUS PoR SURPACI'NG PLATE GLASS Fi1ed'sept..1,19ss A ssheets-sneet 2 Figi?. r"

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May 15, 1934. F. v. WILHELM Er Al. 1,959,225

l I PROCESS AND `APPARATUS FR SURFACING PLATE GLASS Filed Sept. l, 1935 3 Sheets-Sheet 3 JM JA;-

I 'VENTOR www M Patented May y15, 1934 PROCESS AND APPARATUS FOR SURFACING PLATE GLASS Francis V. Wilhelm and Thomas K. Gregorius, Creighton, Pa., assignors to Pittsburgh Plate Glass Company, a corporation of Pennsylvania Application September l, 1933, Serial No. 687,771

` claims. (ci. 51-24m The invention relates to a process and apparatus for surfacing plate glass and particularly to a method of maintaining the tops of the cars or tables which pass beneath the grinding and 5 polishing runners in the straight away surfacing A operation in a true horizontal plane. During the polishing operation, considerable heat is developed due to the relatively high frictional contact between the polishing pads and the glass. l0 This heat is transmitted to the metal plates constituting the tops of the tables and causes them to bulge up slightly at the center so that the surfaces which carry the glass are no longer in a true horizontal plane. This condition corrects itself in part during the return of the tables to the grinding end of the line after the polishing operation, but some convexity still remains, and when the table is again passed beneath the grinding runners (carrying thereon a new plate' of glass or one which has been surfaced only on one side) the glass plate is reduced to uneven thickness, being ground thinner along the middle portion than along the edges at the sides of the table. The object ofthe present invention is to overcome this difficulty by eliminating the bulging or warping of the table tops between successive surfacing operations, so that the table tops are perfectly true and i'lat during each grinding operation. Certain embodiments of the invention are illustrated in the accompanying drawings, wherein:

Figs. 1, 2 and 3 illustrate one form of the apparatus, Fig. 1l being a longitudinal section, Fig. 2 a transverse section on the line II-II of Fig. 1, and Fig. 3 a partial plan view. And Figs. 4, 5, 6 and 7 illustrate modications, the views being in all `cases transverse sections similar to that of Fig. 2.

Referring to the construction of Figs.'1, 2, and

3, 1 is one of a series of glass surfacing tables, to Whose upper side sheets of glass are secured by means of plaster of pars, and which are carried beneath a series of grinding and polishing machines, not shown; 2 is the return-'track along which the cars are carried by any suitable means from one end of the grinding system to the other. As shown, the cars are provided on under sides with racks 3, which are engaged by suitable driving means 4 (Fig. 2) for moving' the train ofv e cars continuously along the track 2.

Located above the line of travel of theucars are a series of sprays 5 connected to a transverse supply pipe 10, so that when the control valve for the pipe 10 is open, the upper and lower surfaces of the plate 11, which constitutes the top of the car or table, are sprayed with water. The valve 12 on the pipe 10 is operated from a 6b solenoid whose coil is supplied by leads 13, 13, and one of these leads is provided with a switch 14 having a roller 15 bearing on the top of the table. While the tables are passing beneath the spraying apparatus, the switch 14 is held in 65 closed position so that the valve 12 is held open. When the tables pass theswitch 14, it opens and the valve l2 is closed, thus cutting oi the supply of water and preventing wastage. In order to dry the tables, conduits 16 and 17 are lprovided eX- 70 `tending transversely of the tables. These pipes are perforated on their sides next to the table and are supplied with air under pressure.

The apparatus as above described provides a means for cooling the table tops 11 rapidly so that 75 any bulge therein incident to the heating effect of the polishers is removed and the upper surface of the top 11 returns to its true horizontal plane before the table is again` assed beneath the grinding and polishing mac 'nes. 80

Fig. 4 illustrates a modication in which the cars 1 are passed through a chamber 18 provided with a series of refrigerating pipes 19 in its upper portion and a plurality of steam pipes'20 lying at a level below the table tops 11. By this means,

the upper surfaces of the tables are cooled and their lower surfaces are heated,vthe amount of cooling and heating being so regulated that the plates 11 are brought to a substantially uniform temperature throughout during the passage of the cars through the chamber 18.

Fig. 5 illustrates a further modification in which the cars 1 are passed through a heat modifying chamber 21. In this case, heat is supplied beneath the table tops by means of the gas `,burners 22 connected to suitable supply pipes 23. By this means, the lower sides of the table tops are' brought to substantially the same temperature as the; upper sides so that anybulge in the tops is removed. In some cases, the heat applied by the burners may be somewhat in excess of that required, and inthat case the series of electric heaters 24 carried by the top of the chamber are used to give lthe additional heat necessary in the tops of the tables. The heaters are supplied by current from the leads 24B. Fig. 6 illustrates a further modification in which the cooling of the tables is accomplished by means of the air jets 24v supplied from the casings 25, 25. Air is forced into the casing from the blower 26 110 through the conduit 27, the fan being operated by the electric motor 28. In order to increase the cooling effect of the air, refrigerating pipes 29 are provided at the entrance end of the casings 25, 25. The cooling effect may also be accentuated by applying some water to the casing 25, 25, this being accomplished by means of the mist sprayers 30, 30 supplied from the pipes 31, 31.

Fig. 7 illustrates still another method of cooling the top plates 11 ofthe cars as they pass along the track 2. The cooling means in this instance comprises an endless belt made up of the metal plates 32, 32 carried upon sprocket chains 33, 33 passing around suitable sprockets and arranged so th'at as the cars pass beneath the endless belt, th'e plates 32 rest upon the tops of the tables and exert a cooling effect thereon. The plates 32 constituting the endless belt are preferably cooled by a series of refrigerating pipes 34 located just above the top iiight of the belt. This belt may be driven or may be movedl merely by contact ofthe lower flight With the tops of the moving tables. The cooling effect Ais such that the top surfaces of the plates 11 constituting the table tops are brought to substantially the same teinperature as the lower sides of these plates so that the plates return to a true horizontal plane.

What we claim is:

1. A process'of treating glass grinding and polishing tables between successive operation which 2. A process of treating glass grinding and polishing tables between successive operation which consists in subjecting the upper faces of the tops thereof to cooling means tending to restore such upper faces of the tables to a temperature approximating that of the lower faces and thus restore the iiatness of the tops.

3. A process of treating glass grinding and pol-f t ishing tables between successive operation which consists in subjecting the lower faces of the tops thereof to heating means tending to bring such lower faces of the tops to a temperature approximating that of the upper faces and thus restore the atness of the tops.

LA process of treating glass grinding and polishing tables between successive operation which consists in subjecting the upper faces of the tops thereof to cooling means and the lower faces thereof to heating means thereby tending to bring the upper faces to a temperature approximating that of the lower faces and thus restore the atness of the tops.

5. In combination in glass surfacing apparatus including tables for carrying glass plates beneath grinding and polishing runners and a return track for the tables, a chamber through which the track extends, refrigerating means in said chamber just above the level of the table topsand heating means in the chamber below the level of the table tops, said refrigerating means in connection with the heating means tending to bring the upper and lower faces of the tables to approximately the same temperature.

FRANCIS V. WILHELM.. THOMAS K. GREGORIUS. 

